SMOLDERING PUMPKINS!

If anyone asks, today our experiment is “an exploration of sublimation using a gourd of theCucurbita genus.”  In other words, we are going to make a smoke-breathing jack-o-lantern using dry ice!

You can usually get dry ice from most major grocery chains.  Just ask for it at customer service.

Before you start–science safety smarts:  This experiment is really cool and lots of fun, but requires an adult assistant.  Before your experiment, keep the dry ice in a cooler with the lid slightly open.  Don’t store it in a tightly closed container, or the rapidly expanding carbon dioxide could burst the container.  It’s also important to remember that you should never touch dry ice with your bare hands—always handle it with tongs or special gloves.  Dry ice is so cold that it can freeze your skin on contact, and it feels like a very bad burn.  Your best bet is to recruit an adult assistant to do the dirty work.

 

Pumpkins-Smoldering (1)

Try it!

To do this experiment, you’ll need a carved pumpkin, some water, some dry ice (a couple of fist-sized pieces will do), and some tongs for picking up the dry ice.  Carve the jack-o-lantern face up high on the pumpkin so the pumpkin will be able to hold water.

Experiment components

Pumpkins-ExpComp

Pour enough water into your pumpkin to cover your piece of dry ice.

Pumpkins-AddingWater

Soren B. adding water to his jack-o-lantern

Last, ask your adult helper to use tongs to put a piece of dry ice into the pumpkin.  Remind your assistant to NEVER touch dry ice with bare hands.

Soren’s adult assistant adds dry ice to the jack-o-lantern with tongs.

Pumpkins-AddDryIce

Voila!  A smoke-breathing jack-o-lantern that is sure to amaze your friends!

Isn’t science great?

How does it work?

Dry ice is solid (frozen) carbon dioxide.  Carbon dioxide (CO2) is what you exhale from your lungs when you breathe out.  At normal room temperature and pressure, carbon dioxide is a gas like the air all around you, but if it gets very, very cold, carbon dioxide freezes and looks like regular ice (frozen water).  Dry ice is different than regular ice though.  For one thing, it is much, much colder.  Water freezes at 32˚F (0˚C), but carbon dioxide has to be cooled down a lot more.  Dry ice is very, very cold—about -100˚F (about -70˚C)!  So why is it called DRY ice?  First, imagine what would happen if you put a bunch of regular ice in a cup and then left the cup out overnight.  What do you think you would find in the cup the next morning?  You would find a liquid.  Melted ice is…water.  Carbon dioxide has a funny property when it is allowed to sit at normal room temperature.  Instead of melting like regular ice, it turns immediately into a gas.  Scientists call this sublimation.  People noticed that the “melting” dry ice didn’t leave a puddle of liquid the way water does, so they called it “dry.”  It’s easier to see dry ice sublimate if you put it a piece in a bowl water.  Water with dry ice in it bubbles and fizzes as the carbon dioxide bubbles rise to the surface and escape as a smoke-like vapor.  Amazing!

Join us again next week for more Halloween experiment fun!

 

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